Fuel tanks are increasingly being manufactured out of weldable polymer materials, such as polyethylene, that lend to efficient manufacturing processes such as blow-molding. The use of these fuel tanks is becoming widespread; however, the prior art has not yet disclosed a suitable structure for connecting fuel tank components to such polymeric tanks. Materials that lend themselves to efficient manufacture of polymeric fuel tanks typically are not suitable for making quality fuel tank components because they are frequently too soft and are subject to long term creep problems.
Moreover, the preferred method for attaching components to polymeric fuel tanks has been to weld them using well-known techniques, such as hot plate welding. The high temperatures used in the welding process can damage components made largely or entirely out of the same material as the fuel tank. However, harder, higher-melting temperature materials such as nylon, which are suitable for use in component construction, are difficult if not impossible to weld to polymeric fuel tanks. For example, polyethylene and nylon simply do not weld well to each other due to their different melting temperatures and other properties.
Moreover, any component that is attached to the tank must be a good hydrocarbon barrier to meet environmental regulations. Weldable materials generally do not make good barriers. To address these multiple requirements, one proposed solution involves providing a fuel tank component made of suitable barrier material, such as nylon, with a weldable connector. The weldable connector is then welded to the fuel tank, thereby attaching the entire component to the fuel tank. One method for providing a weldable connector on the component body involves overmolding a weldable connector onto an upper portion of the component housing (or vice versa). This connector is initially manufactured as a component separate from the housing and has a different melting temperature and welding properties than the component housing to allow it to be easily welded to the fuel tank.
The connector and the component housing must be securely connected to each other to prevent fuel vapor permeation, fuel wicking between the connector and the housing, and mechanical separation of the connector from the housing. However, certain problems are inherent in attempting to connect or mold the weldable material of the connector to the non-weldable material of the housing. The materials normally used, such as polyethylene and nylon, typically do not adhere very well, resulting in a weak interface between the two.
Currently known structures rely on a mechanical interlocking connection between the connector and the component housing via overmolding or insert molding to create a more secure interface. The interlocking connection causes at least a portion of the connector to be surrounded by the component housing or vice versa, but in either case, the complicated configuration needed to form the interlocking connection requires complex tooling that increases the manufacturing cost of the component.
There is a desire for a component structure that provides improved sealing and connection properties between the housing and the connector and that is simpler and less expensive to manufacture than currently existing structures requiring an interlocking connection between the housing and the connector.